It's not a big deal,really.Both the standard and Magic Aire will get you warm,bye-and bye.The magic Aire draws in fresh air, and is supposedly more efficient ,especially at removing moisture laden air from the cab.Can't say if it's true, I've only ever had this one Fridge.

I can tell you this:If you have the chance to get the cardboard defrost outlets from old 57-60 trucks,grab them.They are often missing or deteriorated to the point of crumbling,and are hard to find.Even in decent condition,they deform over time and usually don't seal well to the dash, leaking air to below the dash area,causing slow windshield defrosting..They often go for high prices on eBay.There's a guy asking 125.00 for a pair in an auction now.